Scared of intimacy

Does anyone else feel like they get to a certain point in dating and they start pulling away?. I've been seeing this guy for a few months now, the sex is great, we're quite similar in personalities, and we have fun together. He treats me well and he's very thoughtful... But last night I left his house really late because I couldn't relax. He seems very keen and has expressed that he has feelings for me..but I don't know if I feel the same way. I have honestly gotten to a point in my life where I don't know if I'm actually capable of truly loving someone. I've only ever seemed to be infatuated by someone. I'm so scared of committing to someone...but why?? Are some people just meant to stay single?